A milling cutter has an axis of rotation and a cutter body with a peripheral face and an end face, the cutter body being formed with a plurality of peripherally formed receiving pockets adapted for releasably receiving a like number of cutting units. The cutting units have operative cutting edges substantially radially disposed in the end face and substantially radially directed abutment surfaces remote from the end face. A milling cutter's operative cutting edges are perpendicular to the axis of rotation to wipe a work surface whose smoothness is a function of the axial distance between its least and most axially outward operative cutting edges, the distance being known as "axial runout".
It is known to provide a milling cutter with a plurality of adjustment devices for the independent axial adjustment of each cutting unit. Each adjustment device comprises screw means engaging an adjustment member directly or indirectly pressing against a cutting unit for positively pushing the same axially outward on rotation of the screw means in a given direction. In contrast, any inward axial displacement of a cutting unit requires an initial rotation of the screw means in the opposite direction prior to the application of an externally inward axial force, for example, as applied by light impacts.
Consequently, axial runout adjustment of a milling cutter typically, but not exclusively, involves the outward axial displacement of its least axially outward cutting units so as to be ideally co-planar with its initially most axially outward cutting unit, whereby axial runout is a desirable zero. In order that adjustment devices are good for a number of axial runout adjustments which may occur regularly as part of a workshop's maintenance schedule, they require periodic re-setting such that all the cutting edges of a fresh set of cutting units yet to be axially adjusted are relatively axially inward.
Of considerable significance is that an adjustment member is suitably shaped and dimensioned so as to be snugly received in a cylindrical bore formed in a cutter body such that it can provide suitable axial support to a cutting unit abutting thereagainst during a machining operation and, at the same time, its seating remains undisturbed during the replacement of a worn cutting unit.
It is known to employ differential screws as screw means in adjusting means for milling cutters, for example, as described in EP 0 282 090 B1 and U.S. Pat. No. 3,195,376, however, such arrangements suffer, in particular, from the disadvantage that the receiving nut portions in a cutter body are required to be of extremely high accuracy for the smooth operation of the adjusting means over their entire adjustment range.
In the specific examples illustrated and shown, the adjustment device of the former includes a substantially cylindrical, elongated, tubular adjustment member with a longitudinally directed, planar adjustment surface inclined with respect to its longitudinal axis such that its radial displacement in a given direction causes an outward axial displacement of its abutting cutting unit. Against this, the adjustment device of the latter includes a conical, elongated, tubular adjustment member with a longitudinally directed, quadrant shaped, curved adjustment surface eccentric with respect to its longitudinal axis such that its rotation in a given direction causes an outward axial displacement of its abutting cutting unit.
In an alternative approach avoiding the use of differential screws, DE 1 175 963 describes a milling cutter with adjustment devices each having a semi-cylindrical, elongated, tubular adjustment member which is displaced radially inward along a support wall inclined towards the end face on the screwing in of an abutting adjustment screw, thereby causing the outward axial displacement of a cutting unit abutting thereagainst. However, no provision is made for the outward radial displacement of an adjustment member on the screwing out of its respective adjustment screw which thereby complicates its replacement, if necessary, and the miller cutter's periodic resetting.